Aryl guanidine-paraformaldehyde reaction product



.. mtfis Pate t No Drawing. Original application May '21, 1956, Ser. No. 585,962, now Patent No. 2,927,051, dated Mar. "1, 1960. Divided-and-this-applicatiomAug. 17,-- 1959, Ser. No. 838,377

2 Claims. CL 260-333) A This invention is concerned withfcornpositions (and iprocesses forl adheringtextiles to rubbers. More specifically, the invention involves compositions and processes for improving the carcass life of pneumatic tires.

In certain IuBber articles designed to withstand considerable stresses in use, the rubber I is reinforced with comparatively inextensible textile materials. Thus, rubber liose, belts and tires are commonly reinforced 1 with fil'2'arrientary textiles' in the 'form of yarns, cordsxor, fabric. fl'n suoh articles, it-is important that thetextile reinforcing inaterialbe firmly adhered to 'the' rubber-and-remain 'efllec- "*tively adliered. even atter I the article has been su'bjected to repeated varying strains in use," because1 any separation -and ae1ative movement of -theruhber andtextile parts le'ads to abrasion "between these parts and consequent earl failure. The' prior art 'methods and' materials'for "adhering textiles to rubber it have ha'd 'a numberof shortcomings, and there has therefore been a continuing desire' for more rtfioient "and satisfactory methdds of 3 providing the re- ""quired adhesion, as evidenced by the large-number of adh'esive p'reparations-in 'commercia1fuseaswell as the grout/ ing"volume oftechnical and patent literature onthis "subject.

Th'e problem i of providing adequate adhesion in "efiicint a'mnher has been particularly acute in the case ofprreumtietires. The best previously known inethod of adheringtire cord to the rubber carcass stockhas" been to apply to" the cord a r solution comprising rubber latex (butadiene-vinylpyridine'copolymer latex being especially sf1ited for' this purpose) togetherwith a partially conde'nse'd resorcinol-formald'ehyde resin and agent oapaible, upo1i hat ing,- if liberating additional formaldehyde in amount 'sufiic-ient' to complete the condensation of the "resin. 'l he tire cord was passed through such a solution 1in the-" form of a webbed fabric or cord fabric, leaving a depos'it not only on 'theexterior surface ofthe cord but also substantially penetrating into the interstices of the cord. -iAfter passing 'fromthesolutioning apparatus the acorn-was introduced into a-long drying and curing oven wherein the water was evaporated from the deposited solution and at the same time the partially condensed resorcinol formaldehyde resin reacted -with the *for'rnaldehyde liberated -by the 'for'maldehyde yieldiiig agent," thereby advancing theresin to a more highly condensed state. Upon completion of'such drying and curing operatiomthe cords, when are now-stifi because of the resin deposit, werepa'ssed through the usual calender, whereFa "thin skim coat of-vulcanizable rubbercarcass stock-was applied to the cord. The resulting rubberized tiredtbridwashsed to-bu'ild up the raw tire casingin -the us'ual way,- and the entire assembly' was subsequently cured in the usual tire mold.

2,981,741 PatentedApr. 25, .1961

The conventional tire cord solutioning process notonly requires extensiveequipment that is expensive to install and maintain, but there also are inherent disadvantages in the process as a consequence of the physical and chemical nature of the adhesive solution. The latex bath is comparativelyunstable and tends to deposit an undesirable -coag u1umover a period of time. The resorcinol-formaldehyde resin-must be; prepared and used with-great-care to provide "consistent adhesion. yeareful controls, variable results are frequently noticed.

Even when exercising The efiicacy of the adhesive solution changes unpredict- --ably.-with age. ,The drying and curing steps are of necesasity time-consuming. Undesirable stifiness 'is imparted to the cord ,fabn'c due to penetration of the latex-resin =so'lution into the interior of the cords, -where solid maten'al is thusdeposited to the detriment of the flexibility andfatigue life of'the cords. The performance of the finally resulting rubber-textile laminate in the finished tire leaves much to be desired, not only from the standpoint of adhesion, but with respect to other characteristics :as

-well, particularly fabric fatigue.

Accordingly, a principal object of thepresent invention .is-toprovide a new and improved compositionuseful for -adhering textilematerials to rubber, anda method. of

certam adhesive-forming components, which may be incorporated into vulcanizable rubber stocks. These rubber stocks subsequently may beapplied to the textiles, and the textile-rubber rubber vulcanizing conditions.

composites thereafter subjected to The textile-rubber adhesive-forming components comprise resorcinol in conjunction with certain aryl-sub- 45 j s titute'd guanidine-formaldehyde hyde reaction product function, per agent. rubber vulcanizing" "conditions. tion anadhesive bond is established between the textile j and the rubber.

reaction products. guanidine-formaldese, as an adhesive However, when employed tconjunctionally in a stock, or by methods described in patent application Serial No. 389,118 to Buckwalter et at, now US. Patent No. 2,746,898 they react chemically under rubber- During the course of the reac- Neither the resorcinol nor the aryl The guanidines that may be reacted with formaldehyde to yieldadhesive-forming compounds with resorcinol include1,3-dia'ryl derivatives having the general formula:

or p) tolyl; etc. PREPARATION OF ARYL GUANIDINE-PARAFOR- MALDEHYDEREACTION PRODUCTS The solid reactants are intimately blended at room of formaldehyde.

. a A P,

temperature in the relative'proportions of 1 molar V "equivalent of water is cleaved for each molar proportion of aryl guanidine present in the original reaction mixture and a free formaldehyde content of the product is less 'than 1% or, preferably, zero.

ALTERNATIVE METHOD OF PREPARATION As an alternative method of preparation, aqueous formaldehyde, e.g., 37% formalin, may be used instead of paraformaldehyde. For example, one molar equivalent of the 1,3-diaryl guanidine is slowly added, with stirring, to formalin containing 5-10 molar equivalents The reactants are then allowed to stand for several hours at room temperature. The aqueous portion of the reaction mixture is removed by decan- 'tation from the insoluble intermediate reaction product and the latter is then processed at 130l50 C. under the conditions described above for the preparatory method employing paraformaldehyde.

' The products, obtained in about 80% yield, are ambercolored, odorless, non-crystalline, pulverulent solids,

having melting points of 60-80 C. They are soluble in common organic solvents and in mineral acids.

The products are believed to be essentially cyclic condensation dimers of 1,3-bis (hydroxymethyl) 1,3-diaryl guanidines. The structure is given below:

-where R is an aryl radical, such as phenyl, tolyl, etc. The adhesive-forming chemicals described above, namely, resorcinol and the 1,3-diary1 guanidine-formaldehyde reaction product may be incorporated into vulcanizable elastomeric materials on conventional-rubbercompounding equipment such as a mill or Banbury. Whatever mixing method may be selected, it is essential for optimum results that the temperature of the stock during mixing and throughout all subsequent'operations 'does not exceed that at which the resorcinol and the 1,3-diaryl guanidine-formaldehyde reaction is initiated. Depending on the time and concentration of the reactants 'in the rubber mix, temperatures as high as 280 F. may

be tolerated.

Although mixing procedures may be varied somewhat,

a preferred method comprises the addition of one of the above components at the beginning, and the other of the components at the end or near end of the mixing cycle. The classes of textile fibers or filaments that can be I adhered to rubbers by use of the composition herein described include native cellulose (e.g., cottons), regenerated cellulose (e.g., rayons), and synthetic linear polyamides (e.g., nylons). The form into which the fibers may be manufactured is immaterial. For example, they may take the form of unspun staple, simple or complex spun yarns, cords, woven fabrics, etc.

stored lndeflnitel for subse uent condensation at or 8; ve 130 0. q p Dodge.

The classes of vulcanizable rubbers to which the textiles can be adhered includenatural rubber (Hevea); synthetic rubbers made by emulsion copolymerization of butadiene-l,3 with styrene, e.g., GR-S, oil extended GR-S; rubber reclaim compositions; etc.

Resorcinol (I) may be introduced into the rubber, or carbon black masterbatch, in its commercially available solid form, as a concentrated aqueous solution, or as a rubber masterbatch. After the introduction of (I) curing aids, accelerators, antioxidants, etc., are then added and are followed by the addition of 1,3-diaryl guanidine-formaldehyde reaction products (II) (granular or powder) and finally sulfur. Table I shows the preferred amounts of (I) and (II) and their practical limits, expressed as parts by weight per parts of rubber hydrocarbon, required for obtaining optimum results.

The ratio of 1/11 should preferably be from 0.3 to 0.5.

A ratio of about 0.4 has been found to be most satisfactory.

Owing to the variable composition of rubbers, the diversity of rubber-compounding chemicals, and of compounding practice, it may be. necessaryto establish by experiment the optimum quantities of (I) and (H) and of curatives etc., that are required for the adequate performance of a given end product.

Vulcanizable rubber stocks containing the adhesiveforming chemicals described above can be reinforced with untreated textiles in the several manufactured forms noted earlier. For example, this sheets or webs of staple fiber in a random or an oriented state may be coated on one or both sides with the adhesive stock to yield nonwoven textile-reinforced rubber; or, the fiber may be incorporated into the rubber by milling, etc., and subsequently sheeted to the desired gauge. When the textile reinforcement is in the form of yarn, cord, woven and weftless fabrics, etc., the rubber coating is applied preferably by passage through a four-roll calender. Although the adhesive-compounded rubber stocks herein disclosed are primarily designed for direct application to grey or untreated textiles, they may be applied, if desired, to textiles previously treated with fluid adhesive compositions.

In many textile-reinforced rubber products there are, m

. addition to the reinforced rubber stock, special purpose non-reinforced stocks which overlie and have a common boundary or interface with the reinforced rubber. For

example, a pneumatic tire contains a reinforced rubber shown in Tables II-V. The results, expressed as dome life, are a measure of therelative resistance of a simulated tire carcass toward ply separation when subjected to severe dynamic strains at temperatures which equal or exceed those attained by tires operating under service conditions. The test data were obtained on the apparatus described in US. Patent No. 2,666,119 to Ernest B.

Table II (I) =Resorcinol.

(II) =1,3-'diphenylguanidine paraformaldehyde reaction product.

Textile=Viscose rayon.

Base rubber stock-:Rubber reclaim.

Adhesive in Latex Ad- Dome Rubber Pts. hesive on Example Life Textile, (ruins) Percent 1 71 None None 6-9 2. 218 2. 4 6.0 None 245 4. 0 10. 0 None 279 6.0 15. 0 None Table III (I) =Resorcino1. (II)=1,3-diphenylguanidine paraformaldehyde reaction product. Textile=Nylon. Base rubber stock=Hevea.

Adhesive in Latex Ad- Dome Rubber Pts. heslve on Example Life Textile, (mins.) Percent (I) (II) 160 None None 6-7 532 2. 4 6. 0 None 605 4.0 0 None 1 1,015 2. 4 6 0 None 1 Nylon cord hot stretched prior to coating with rubber stock.

Table IV (I) =Resorcinol. (H) =1,3-diphenylguanidine-formalin reactlon product. Textile=Viscose rayon. Base rubber stock =Rubber reclaim.

Adhesive in Latex Ad- Dome Rubber Pts. heslve on Example Life Textile, Percent 9 71 None None 6-9 10 210 2. 4 6. 0 None Table V (I) =Resorcinol.

(II) l,3-di-o-Toly1guanidine-paraformaldehyde reaction product.

Textile=Viscose rayon.

Base rubber stock=Rubber reclaim.

Adhesive in Latex Ad- Dome Rubber Pts. heslve on Example Life Textile, (ruins) Percent 11 71 None None 6-9 12 190 4. 0 l0. 0 None Thus, in more detail, one of the adhesive-forming chemicals, such as the resorcinol, may be mixed with the rubber stock, and the other component, the 1,3-diaryl guanidine-formaldehyde reaction product, is applied to the textile.

Regardless of the method of applying the adhesiveforming components to the rubber or to the textile or both, it is essential that the textile and the rubber be brought together before the resorcinol and 1,3-diary1 guanidine-formaldehyde reaction product reacts with each other. During the subsequent vulcanization of the rubber, these two components react to form an excellent adhesive bond between the textile and the rubber.

From the preceding data it will be apparent to those skilled in the art of tire manufacture that the invention affords an unusually effective and convenient way of forming the required adhesive bond between the tire fabric and the rubber carcass stock.

It should be noted that one advantage of the present invention resides in the use of 1,3-diaryl guanidine-formaldehyde reaction products as one of the adhesive-forming components. This reaction product is non-volatile, so that at the reacting temperatures, there is no danger of evolution of any noxious ortoxic vapors.

Another advantage of the present invention is that the use of these aryl guanidine-formaldehyde reaction prod- 'ucts elevates the initiation reaction temperature with re sorcinol above conventional mixing temperatures. Therefore, no special precautions are required during the mixing operation except as noted in column 3, lines 49-56, and it becomes commercially feasible to compound rubber stocks with the adhesivc-forming components at or near the standard milling temperatures (230-280 F.).

This is a continuationeis-part of our above-mentioned copending application Serial No. 389,118, filed October 29, 1953, now U.S. Patent No. 2,746,898, and a division of our copending application Serial No. 585,962, filed May 21, 1956, now U.S. Patent No. 2,927,051.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

1. A chemical having the formula Rs NE Br where R, and R are aryl radicals selected from the group consisting of phenyl and (o, m and p) tolyil.

2. The method of preparing an aryl guanidine-paraformaldehyde reaction product comprising intimately blending a reaction mixture consisting of a solid 1,3-diaryl guanidine, said aryl radicals being selected from the group consisting of phenyl and (o, m and p) tolyl, with solid paraforma-ldehyde, the paraformaldehyde being present in such quantity that 2 to 3 molar equivalents of formaldehyde are provided for each molar equivalent of 1,3-diaryl guanidine, heating the reactants at a temperature of -95 C. until they become fluid, raising the temperature of the reaction mixture to from to C. and providing vigorous agitation, to thereby cleave one molar equivalent of water for each molar proportion of the 1,3-diary1 guanidine present in the original reaction mixture, the reaction being completed when the free formaldehyde content of the reaction product is less than 1%.

OTHER REFERENCES Geigy: Chem. Abs., vol. 44, p. 848 (1950). 

1. A CHEMICAL HAVING THE FORMULA 